The invention relates to contact bumps on microstructure fabricated (MF) transducers. In particular, the invention relates to reducing chemical contamination from contact bumps in MF transducers used in disc drives.
In microstructure fabricated (MF) transducer assemblies, such as those used in disc drives, soldering is used to make electrical connections between the MF transducer and external wires or cables. Contact bumps are formed on the MF transducer assembly and soldered to contact pads on a flexible printed circuit. Soldering is a preferred connection method because it provides reliable electrical connections that are small in size and that can be conveniently completed using reflow solder.
Contact bumps are formed of tin, or copper that is plated with tin or solder to enhance solderability. Tin or solder, however, can diffuse during MF vacuum manufacturing processes such as vapor deposition, doping, sputtering and the like. The diffusion of the tin or solder can contaminate processing equipment such as vacuum chambers during the manufacturing processes. Contact bumps are thus added in a separate process step after the vacuum processes have been completed to avoid damage from chemical contamination.
Applying the contact bumps requires moving the transducer assemblies from a contamination-free MF manufacturing environment to an area where the contamination is tolerable. The high levels of precision alignment and automated batch fabrication that are available in MF processes are not available to apply the contact bumps. The contact bump operation is done with less precision and is considerably more costly because it is done in an extra step after the MF vacuum manufacturing processes.
A MF transducer assembly, and a method of manufacturing a MF transducer assembly are needed in which contact bumps can be present within the MF manufacturing environment without contaminating MF vacuum processes.
A method of manufacturing a transducer assembly is disclosed in which an electric current is passed through plating solution in recesses of a metal substrate to plate contact bumps. The contact bumps have bump fronts in the recesses and have bump backs that are exposed. The bump fronts are covered with a sealing layer that blocks diffusion during MF vacuum processes. A transducer is partially formed on the substrate, sealing the exposed bump backs. One or more vacuum processes are performed to complete formation of the transducer. At least a portion of the metal substrate is etched away to expose the bump fronts of the electrical contact bumps.